Phytogeographical relations in the. de Smidt. the mineral content of the soil, and human. of the Eastern-Veluwe. Here. where the heath consists

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1 Phytogeographical relations in the North West European heath JT de Smidt (Botanical Museum and Herbarium, Utrecht) {received December nd, ) Introduction The water economy, the mineral content of the soil, and human influence are the principal ecological factors governing of the heath vegetation of a limited region Sloping the variation of the surface is also an important factor In hilly country it is of a twofold nature: on the one hand the difference between high and low altitudes, based on the water economy, on the other hand differences in (micro) climate If the hills are higher, this results in climatic differ greater ences In extremely oceanic and in boreal regions a rise in altitude of 00 m is sufficient for creating a noticeable decrease in temperature and an increase in precipitation, aerial moisture, and wind force This results in the occurrence on the hills of heath communities that have their main distribution more to the North The same observation was made by Gimingham () On Slieve League on the Donegal coast (Ireland) Salix herbacea and Lycopodium selago occur in the heath at an altitude of 00 m, near Tongue on the Scottish north coast Dryas octopetala, Saxifraga oppositifolia, Alchemilla alpina and Thalictrum alpinum at an altitude of 0 m West of Apeldoorn in the Netherlands are foundextensive stretches of heathwith abundant Vaccinium myrtillus and V vitisidaea at an elevation of 00 m, even on southfacing slopes This is an area with high precipitation due to ascending air west of the hill ridge of the EasternVeluwe Here the Vacciniums, elsewhere requiring the protection of the forest, can tolerate the habitat of the heath open (Stoutjesdijk, ; De Smidt, ) Higher elevation combined with northfacing slopes creates extreme conditions eg on Roc Trévézel (000 m) in Brittany, with Vaccinium myrtillus, Melampyrum pratense, Hymenophyllum wilsonii and Rhytidiadelphus loreus These are species virtually lacking in the surrounding plains where the heath consists of such South Atlantic species as Erica cinerea, E ciliaris, Ulex gallii, Lobelia urens, Lithospermum prostratum and Symethis planifolia in Conversely, protected valleys and on richer soil we find more southerly communities to the North of their main area In the Maas valley between Maaseik and Maastricht a of loss, rich in minerals and with a mild local climate supports a of Calluna vegetation 0 m high with as codominant species Sarothamnus This scoparius is a subatïantic community with Southern and Central European tendencies, mainly developed in low mountains: Eifel, Black Forest, 0

2 PHYTOGEOGRAPHICAL RELATIONSIN THE NORTH WEST EUROPEAN HEATH and in a modified composition the on Plateau Central (De Smidt, ) Often it is the interaction between local climate and soil conditions that provides a suitable habitat for such extrazonal communities, as is the case with this CallunaSarothamnus heath On Roc Trevezel the local climate is the main factor An extrazonal heath due to soil conditions is the poor Calluna heath with Hypnum cupressiforme var ericetorum, Festuca ovina, Carex pilulifera on deep sandy deposits at Revingehed, East of Lund (South Sweden) This is common in Northern the Belgium, Netherlands, and Northwest Germany with its northern border in South Jutland A striking phenomenon is the absence of boreal species that are common in the heath of the region: Vaccinium myrtillus, V vitisidaea, Cornus suecica, Trientalis europaea, Lycopodium clavatum This paper chiefly deals with the phytogeographical characteristics of the zonal heaths This term is employed for the main s in the Western European heath vegetation that can be distinguished on the basis of phytogeographical spectra The criterium for delimiting geographically these main vegetation s is the presence of a group of species with a similar distribution Since the distribution of the species is chiefly due to climatic factors, the area of the main vegetation s, too, depends chiefly on the macroclimate Bocher () was the first to employ of distribution spectra s for classifying the European heathvegetations Schubert (0) also suggested a classification mainly based upon phytogeographic characters Gimingham (), too, made some phytogeographical conclusions in his study on the variation of floristic composition and quantitative estimates of cover in the North European heath communities The distribution of the species in the north west european heats In Tables are listed the total number of species which have been recorded by the author in the North West European heath In each separate column all those species are enumerated which were recorded in a certain of part Western Europe Initially smaller areas had been listed separately, but several could be combined because of their This great similarity was the case with Scotland and Wales, and with the Northern Netherlands, Northwest Germany, and Southern Jutland The following distribution s are distinguished in the tables a widely distributed b subatlantic c atlantic d mediterranean atl e euatlantic f borealatlantic g borealmontane h arcticalpine i centralmeridional j continental The overall species list can be subdivided into four groups

3 gracilis sylvatica floerkeana verticillata cornutoradiata rangiformis macilenta pityrea canina stolonifera compactum papillosum plumulosum J T DE SMIDT Table Species widely distributed in the NorthWest European heath Distribution Region no *) 0 a Calluna vulgaris Festuca ovina Molinia caerulea Hypnum cupr Pleurozium schreberi v ericetorum, Dicranum scoparium Polytrichum commune Aulacomnium palustre Cladonia uncialis v pyx chlorophaea crispata furcata squamosa cocc v pleurota Parmelia physodes Cornicularia aculeata Peltigera canina Leucobryum glaucum Polytrichum piliferum, Polytrichum juniperinum Scleropodium purum Sphagnum molluscum Lophocolea bidentata, Ptilidium ciliare Cephaloziella sp Orchis mac ssp ericetorium Succisa pratensis Viola riviniana Carex nigra Salix repens Agrostis tenuis Solidago virgaurea Thymus serpyllum Lotus corniculatus Juniperus communis Rumex acetosella Scapania nemorosa Plantago lanceolata Rumex acetosa Prunella vulgaris *) For explanation of region no s see Table, p

4 Cladonia Potentilla erecta Luzula campestris PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH Table ( continued) Distribution Region no 0 Linum catharticum Sphagnum acutifolium Rhytidiadelphus squarrosus Polytrichum strictum Hieracium pilosella Campanula rotundifolia Luzula multiflora Sorbus aucuparia Gymnocolea inflata destricta Festuca rubra Holcus lanatus Achillea millefolium Frangula alnus Quercus robur Anthoxanthum odoratum Mnium hornum Antennaria dioica Poa pratensis Genista tinctoria Cetraria glauca Cladonia glauca Barbilophozia barbata Hylocomium splendens Veronica officinalis Platanthera bifolia Hieracium umbellatum b Galium saxatile Carex pilulifera Carex panicea Nardus stricta Sieglingia decumbens Cladonia impexa Drosera intermedia Pedicularis sylvatica Hypochoeris radicata Euphrasia micrantha Carex echinata Viola canina Oxalis acetosella Anthyllis vulneraria Deschampsia flexuosa Polygala serpyllifolia Gentiana pneumonanthe Cuscuta epithymum Lonicera periclymenum Diplophyllum albicans Frullania tamarisci Sarothamnus scoparius Carex pulicaris Lophozia ventricosa Calypogeia trichomanes

5 T DE SMIDT J Table (continued) arcticnouncedly mediterranean, alpine, continental or extremely atlantic distribution, the area under consideration being situated in Distribution Region no 0 Odontoschisma sphagni Orthocaulis attenuatus c Narthecium ossifragum Juncus squarrosus Erica tetralix Myrica gale Silene maritima Rosa pimpinellifolia Genista anglica Campylopus flexuosus f Scirpus caespitosus g Vaccinium myrtillus,, vitisidaea,, oxycoccus Arctostaphylos uvaursi Empetrum nigrum Pinus sylvestris Betula pubescens,, verrucosa Populus tremula Rhynchospora alba Eriophorum angustifolium,, vagina turn Drosera rotundifolia Melampyrum pratense i Jasione montana Armeria maritima Filipendula hexapetala Rhacomitrium canescens Species widely distributed in the heath Table These species occur in all ten areas or, if in less, then without clear preference for certain ones among them To this group belong species, more than one third of the total number recorded in the heath Nearly 0 % of them are not only widely distributed in the North West European heath, but also in the rest of Europe and Asia, and often as well in North America More than 0% have a subatlantic area; this is much more than in the three other groups This shows that the widely distributed and the subatlantic form the connecting element in the heath formation of the North West European plains Besides there are smaller numbers of the borealmontane (0%) and the atlantic (%) distribution It is clear that in this group we do not find any species with pro

6 PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH the atlantic and subatlantic region from Southern Scandinavia to Central France and from Ireland to North Germany Less obvious is the scarcity of species with Central or South European tendencies Among the four species placed in this category two, viz Jasione montana and Armeria maritima, are polymorphic and comprise oceanic forms: Jasione montana ssp maritima in the coastel heath of Ireland and Brittany and the coastal form of Armeria maritima in Brittany, Scotland, and Southern Scandinavia A striking phenomenon is the rather high percentage of the borealmontane element (0%) It consists partly of trees of the borealmontane woods, Pinus, Betula and Populus tremula, that reach rather far South in Central and Western Europe on poor soils in the plains A few species that form part of these woods in the undergrowth, Vaccinium myrtillus, and V vitisidaea, and Melampyrum also pratense, occur in the heath As they penetrate more southerly regions, they are more strictly confined to the cool and moist microclimate of the woods In Scandinavia and Scotland the macroclimate permits their frequent occurrence in the open heath, outside the protecting woods In the heath of Northern Germany and southward they are confined to northfacing slopes and to hilly country with a cool moist microresp local climate The rest of the borealmontane species of this group are plants of peat bogs except Arctostaphylos uvaursi In the oligotrophic peat bogs and boggy heaths of the Dutch and German lowland, of Brittany and the British Isles they find a suitable habitat far to the South of their main area Böcher () calls the distribution of Arctostaphylos uvaursi very problematic, as it is frequent both in extremely oceanic regions (Western Norway, Scotland, Northern and Ireland) in rather continental areas in the northern part of Central Europe As a possible explanation Bocher suggests the existence of different bios originating from populations that survived the glaciation under different climatic conditions Species with preference for northern heaths Table Scotland, Western Norway, Southern Sweden, Northern Jutland Widely distributed, atlantic and subatlantic are species reduced to half the in the percentage preceding group In the other hand the portion of borealmontane species is more than twice as high The borealatlantic element is also strong: out of species with this of distribution occurring in the North West European heath belong to this group The arcticalpine element is, however, lacking as it is confined to group C, Table : species with a more westerly distribution in the heath Apart from the boreal flora element it is the continental element (%) that particularly characterises this it is group; virtually absent from the others Within the group of northern heathland species a shift in the flora elements may be observed as one moves eastward In Scotland the borealmontane element (Table, g) comprises

7 arenaria J T DE SMIDT Table Species with preference for northern heaths Distribution Region no 0 a Epilobium angustifolium Rhytidiadelphus triquetrus Bazzania trilobata Lophozia bicrenata Ranunculus acer Dicranum polysetum spurium Pohlia nutans Galium verum Polygala vulgaris Fragaria vesca Lophocolea heterophylla Hieracium laevigatum Vicia cracca Stellaria graminea Trifolium repcns Silene cucubalus Hypericum perforatum Plagiothecium denticulatum,, Orthocaulis lycopodioides Hypericum maculatum Silene nutans Briza media Trifolium arvense Knautia arvensis Erigeron acris Centaurea scabiosa Medicago falcata b Veronica chamaedrys Genista pilosa Juncus balticus Lycopodium inundatum Rosa tomentosa Sedum telephium Scleranthus perennis Ononis spinosa Ornithopus perpusillus c Potentilla anglica Carex trinervis r Pinguicula vulgaris Anemone nemorosa Luzula pilosa Cornus suecica Convallaria majalis Ajuga pyramidalis Rhynchospora fusca Sorbus hybrida Lathyrus montanus Leucorchis albida Ligusticum scoticum

8 linnaeana phcgopteris PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH Table ( continued) Distribution Region no 0 g Lycopodium clavatum Getraria islandica Majanthemum bifolium Polypodium vulgare Trientalis europaea Vaccinium uliginosum Cladonia rangiferina Dryopteris spinulosa Galium boreale Lycopodium annotinum Equisetum sylvaticum Sphaerophorus globosus Evernia prunastri Andromeda polifolia Cladonia bellidiflora Orthocaulis kunzeanus Cladonia alpestris Cetraria juniperina Splachnum ampullaceum i Leontodon autumnalis Carex montana Rosa dumetorum Saxifraga tridactylites Melica nutans Polygonatum odoratum Dianthus deltoides j Scorzonera humilis Arnica montana Hypochoeris maculata Trifolium medium Carex ericetorum Pimpinella saxifraga Anemone pulsatilla Vicia cassubica Viscaria vulgaris Helictotrichon pratensis Prunus spinosa Cladonia mitis Genista germanica Carex caryophyllea Artemisia campestris Helichrysum arenarium approximately as many species as in most parts of Scandinavia The representation of the other flora elements is, however, much weaker, as calculated from the species that have a northern distribution in the heath Instead, Scotland possesses some arcticalpine, euatlantic, and a few mediterraneanatlantic species (see Table )

9 T DE J SMIDT Western Norway has more borealatlantic species in the heath than Scotland, but in terms of the other elements it has more in common with the last named country than with the rest of Scandinavia the Floristically speaking too, Western Norwegian heath is closer to the British than to the Scandinavian See especially Table which lists some typically western species from Western Norway: Erica cinerea, Hypericum pulchrum, Carex binervis, Juniperus nana, Blechnum spicant, Mylia taylori, Bazzania tricrenata, Anastrepta orcadensis, Breutelia chrysocoma, Campylopus atrovirens Eastward the continental element is first encountered in the Dutch German plain It increases in North Jutland and reaches its peak in the region under study in South East Sweden (%) The same is true for the centralsouthern European species Bocher () lists the same species from the Eastern Danish heaths and Schubert (0) from the Central European heaths The most widespread continental species are: Pimpinella saxifraga, Scorzonera humilis, Arnica montana, Hypochoeris maculata, Carex Anemone ericetorum, pulsatilla and Cladonia mitis The of presence Scorzonera humilis in the Breton heath is a phytogeographical and ecological enigma This species is common in Central Europe where it shows a predilection for mineral rich, dry, and often warm habitats It decreases in general toward the atlantic side, except in Brittany where it reaches a second optimum Contrary to what may be expected it does not occur in the driest habitats, but in very boggy heath Probably it belongs to a different eco than the Central European plant Species with preference for western heaths Table As far as heath is concerned these species have their optimum in Northern Ireland, Wales, Scotland and Western Norway Characteristic is the optimal representation in the heath of the euatlantic and the arcticalpine flora element Of the recorded euatlantic heathland species belong to the present group The four other species show preference for the southatlantic heath of Southern Ireland and Brittany The western heath shares a relatively high percentage of borealmontane species (0 %) with the northernheath (%) The arcticalpine species are confined to this group It mainly comprises to sealevel on the North coast of species descending Scotland ( Saxifraga oppositifolia, Thalictrum alpinum, Dryas octopetala, Alchemilla alpina), or at least to low altitudes (Èmpetrum hermaphroditum, Lycopodium alpinum) Salix herbacea was met with in the heath of the Irish North West coast and Juncus trifidus on the West coast of Norway The habitats are always exposed to strong wind and face the sea directly The almost strong, continuously blowing wind is probably the most important factor governing the presence of these species In combination with the and the mostly high atmospheric humidity low summer temperatures an environment is created that shows certain similarities to mountain conditions

10 cuspidatum PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH Table Species with preference for western heaths Distribution Region no 0 a Cladonia strepsilis Telaranea setacea Cephalozia bicuspidata Mylia anomala Lepidozia reptans Thuidium tamariscinum Brachypodium pinnatum Pteridium aquilinum ssp aq Rhinanthus minor Sphagnum rubellum recurvum b Schoenus nigricans Cladonia papillaria degenerans Juncus acutiflorus Hedera helix Lysimachia nemorum Aquilegia vulgaris c Cirsium dissectum Scapania gracilis Digitalis purpurea Ilex aquifolia Blechnum spicant Rhytidiadelphus loreus Dicranum majus Plagiothecium undulatum Rhacomitrium lanuginosum Campylopus brevipilus Plantago maritima d Ulex galli Pinguicula lusitanica Teucrium scorodonia Luzula maxima Endymion nutans Lejeunea cavifolia e Hymenophyllum wilsonii Thymus drucei Plagiochila spinulosa Pleurozia purpurea Herberta hutchinsiae Mylia taylori Bazzania tricrenata Anastrepta orcadensis Breutelia chrysocoma Lophozia quinquedentata Carex binervis Hypericum pulchrum Campylopus atrovirens Erica cinerea

11 irrigua subcervicornis styctophyllum 0 T DE SMIDT J Table ( continued) Distribution Region no 0 Cladonia tenuis Nowellia curvifolia Lepidozia pearsonii Hieracium schmidtii Scapania compacta Plagiochila denticulata Mastigophora woodsii f Juniperus nana Festuca vivipara g Gentianella campestris Listera cordata Lycopodium selago Selaginella selaginoides Ptilium crista castrensis Sanguisorba officinalis Rubus chamaemorus Pyrola rotundifolia minor Trollius europaeus Dryopteris filixmas Sphagnum robustum Dicranum bonjeani Cladonia flabelliformis Stereocaulon paschale Linnaea borealis h Alchemilla alpina Salix herbacea Empetrum hermaphroditum Saxifraga oppositifolia Thalictrum alpinum Dryas octopetala Lycopodium alpinum Juncus trifidus The overall percentage of atlantic species in this group is, that of the northern species ; continental species are lacking The difference with the preceding group with percentages for these elements of,,, respectively, is evident The western heath is of a much more extreme nature than the northern heath The percentages for the northern heath show it to be a meetingground of atlantic, boreal, and continental species The percentages of widely distributed species in the northern and western heath are and, respectively This again reflects the extreme nature of the lastnamed vegetation

12 ciliaris aemula PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH Species with preference for SouthAtlantic heaths Table The optimal development of these species, as far as their occurrence in the heath is concerned, is in Southern Ireland, Cornwall, Brittany and outside of the region studied till the present, more to the South in the coastal regions of the Bay of Biscay The low percentage of the widely distributed species (%) shows that this group, too, shows a strong preponderance of a certain element with a specialised character, in this case the mediterraneanatlantic element which comprises % of the species The species with an atlantic tendency in their distribution make up together %of the group The total is, much less than in the preceding groups, where it is and, respectively Future studies in the heath South of Brittany will probably show this number to be much higher Table Species with preference for southatlantic heaths Distribution Region no 0 a Leontodon hispidus Chrysanthemum leucanthemum Stachys betonica Ranunculus flammula b Radiola linoides Hypericum humifusum Sorbus torminalis Serratula tinctoria Carex flacca c Scilla verna Cladonia imp v leucophaea Corydalis claviculata Hypericum helodes Dryopteris borreri Saccogyna viticulosa Adelanthus decipiens d Erica vagans x watsoni Agrostis setacea Scilla autumnalis Salix atrocinerea Ulex minor europaeus Anagallis tenella Scutellaria minor Parmelia trichotera Lotus corniculatus ssp maritimus Daucus gummifer Euphorbia portlandica paralias

13 mackai spathularis J T DE SMIDT Table ( continued ) Distribution Region no 0 Senecio cineraria Rubia peregrina Asparagus off ssp prostratus Dactylus glom ssp hispanica, Cirsium filipendulum Symethis planifolia Ruscus aculeatus, Lithospermum prostratum Hypericum linarifolium Helianthemum umbellatum Tuberaria guttata Astrocarpus purpurascens Lobelia urens Carum verticillatum Sphagnum pylaiei Asphodelus arrondeaui sphaerocarpus Orobanche cruenta Potentilla splendens Erica scoparia, Cladonia endiviaefolia Sedum anglicum Pyrus cordata Erica mediterranea Daboecia polifolia Koeleria albescens e Cochlearia officinalis Erica x praegeri Saxifraga umbrosa j Allium schoenoprasum The spectra of distribution s In the groups through 0 in Table all plant species have been compiled that were found in the heath of the regions under consideration Ten different distribution s were In distinguished most of the regions the widely distributed species form ca 0% of the total set of species; the subatlantic element is also rather evenly The represented (%) borealmontane element, too, is always but shows much wider variation present, (%) To these three flora elements belong of species (= %) the total number of recorded by the author in the North West European heath vegetations This clearly demonstrates the affinity the heath among regions studied The other flora elements absent are from one or more regions or have a representation of On the % only basis of the distribution of the last named flora elements, five regions may be distinguished

14 PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH Scotland and Wales, WestemNorway j borealatlantic SouthernNetherlands and Belgium NorthernNetherlands, N Germany/ NorthernJutland I subatlantic SouthwestSweden j boreai subatlantlc 0 SoutheastSwcden borealsubcontinental Brittany j SouthemEngland [ Southatlantic Ireland J Table Spectra of distribution s of the heathland species recorded in 0 NorthWest European regions Region no (%) 0 (number of species) 0 widely distributed subatlantic 0 0 atlantic 0 0 mediterranean atl 0 euatl antic 0 borealatlantic 0 borealmontane arcticalpine centralmeridional continental Total 0 J J! 0

15 J T DE SMIDT Group Species with preference for southatlantic heaths Species with preference for western heaths Species with preference for northern heaths Species widely distributed in the NorthWest European heath The total number of species () listed in the NorthWest European heath Table Spectra of distribution s of the NorthWest European heathland species, according to their geographic preference devided in four separate groups Group no (%) (number of species) a widely distributed b subatlantic 0 c atlantic d mediterraneanatlantic e euatlantic f borealatlantic g borealmontane 0 0 h arcticalpine i centralmeridional j continental Total number

16 PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH The southatlantic region Table a, no,, Brittany, Southern England, and Ireland Here the atlantic and the mediterraneanatlantic element have their optimum; the euatlantic element is also well represented The flora elements with boreal or continental areas are much weaker represented than in other regions The South Atlantic character is most pronounced in Brittany with % of mediterraneanatlantic species The overall percentage of species with atlantic affinities in Brittany is % (0 species); consequently the percentage of widely distributed species ( %) is much lower than elsewhere, but the absolute number of species of this, 0, is not below the average The borealatlantic region Table, no and Scotland, Wales and SouthWestern Norway The euatlantic element is well represented, as in the southatlantic region, but there is much less of the less extreme western flora elements, viz the atlantic and the subatlantic; this is naturally more true for the mediterraneanatlantic The boreal ties are much stronger: the borealatlantic the borealmontane, and the arcticalpine flora element together comprise % (in the preceding region %) The presence of arcticalpine species in this region has been noted already ( ) The subatlantic region Table, no and Belgium, Netherlands, NorthWestern Germany, Southern Jutland In this region the heath is notable by the absence of species reaching their optimum This becomes evidentwhen Tables en are compared Group (Table ) has its optimum in the southatlantic (Table, no,, ), group in the borealatlantic (Table, no, ), group in the borealsubatlantic (Table, no, ) and in the borealsubcontinental region (Table, no 0) In Table a group with its optimum in the subatlantic region could not be distinguished Most constituents of the heath vegetation are widespread in this kind of vegetation in NorthWestern Europe Only the continental species in the northern part of the region are aberrant The overall number of species is strikingly low in the southern part,, slightly more than half the number of the northern The difference is part mainly due to the presence of continental species and of a larger number of species with a northern of distribution on mineral rich soil, coastal and woodland species; but these are distributed among the flora elements in such a way that the constitution of both parts, relatively speaking, differs but little The larger number of species with a northern of distribution is not only due to the more northerly position but also to the Riss glaciation The glaciers formed push moraines whose northfacing slopes provide favorable habitats for northern species (Lycopodium clavatum, Polypodium vulgare, Trientalis europaea, Vaccinium vitisidaea, Arctostaphylos uvaursi) and woodland

17 T DE J SMIDT species (Dryopteris spinulosa, Anemone nemorosa, Hieracium laevigatum, Lonicera periclymenum, Hylocomium splendens) The glaciers also deposited richer soils, boulder clay and consequently the heath contains more species than on the poor coversands to the South Heathland species of the better northern soils are Succisa pratensis, Campanula rotundifolia, Luzula multifiora, L campestris, Antennaria dioica, Platanthera bifolia The presence, in the northern part, of coastal species {Rosa pimpinellifolia, Carex trinervis, Carex arenaria, Genista tinctoria) is due to the absence of lime in the sand of the coastal dunes North of Bergen on the Dutch coast The coastal dune heath is well developed from Bergen to Cape Skagen but is absent from the dunes with a higher lime content to the South of Bergen and on the Belgian and northern French coasts It does not reappear until Normandy, but here on the cliffs of acid rocks rather than in the dunes which are also rich in lime The borealsubatlantic region Table, no, Northern Jutland, SouthWestern Sweden The phytogeographic spectra of this region show a characteristic combination of a rather high percentage ( and %, respectively) ofboreal species with relatively rather many species with a continental or a centralsouthern European tendency ( and %, respectively) The percentage of atlantic species is lower than in the preceding regions The borealsubcontinental region Table, no 0 SouthEastern Sweden The continental tendency, low in the subatlantic region and slightly in the borealmontane stronger region, is most noticeable in the NorthWest European heath in SouthEast Sweden (Damman, ) and in Eastern Denmark (Bocher, ), an offshoot of the subcontinental heath of Eastern Germany and Poland (Schubert, 0) The total number of species (0) is the lowest in the regions studied, in the Southern Netherlands except and Belgium This is partly due to the smaller size and consequently smaller variation But the main reason is probably the climate The annual precipitation in SouthWest Sweden is mm, in the heath areas of South East Sweden only 0000 mm (Damman, ) The formation of humus and leaching take place so intensively in the south western part that heath may occur even on originally neutral or even basic soils Such heaths can be recognized by its herbrich with aspect Scorzonera humilis, Orchis maculata, Succisa pratensis, Solidago virgaurea Lathyrus montanus, Sieglingia decumbens Potentilla erecta In South East Sweden, however, such habitats are occupied by grassland of a continental with Anthericum ramosum, Helichrysum arenarium, Anthyllis vulneraria Androsace septentrionalis, Satureja acinos, Artemisia campestris and Medicago falcata Here the heath covers the poor soils,

18 PHYTOGEOGRAPHICAL RELATIONS IN THE NORTH WEST EUROPEAN HEATH also with continental species (%): Vida cassubica, Viscaria vulgaris, Anemonepulsatilla, Artemisia campestris, Helichrysum arenarium The atlantic influence is the lowest of all areas studied ( %) The boreal influence (%) is weaker than in the Southern Netherlands and Belgium and approaches that ofireland and Southern England An arithmetical consequence of this low percentage is the high amount of widely distributed species, % The numerical relations between the flora elements and the low overall number of species show that the heath is here near the border of its distribution The flora is quantitatively and qualitatively poorer than in the other regions; the only addition is the continental element, mostly consisting of grassland species This shows a transition to the dry continental grassland vegetation The same transition was described by Schubert (0) for Central Germany ACKNOWLEDGMENTS The data used in this paper were collected during the following journeys: Netherlands, Belgium, North Western Germany (), Eire and Northern Ireland (), Brittany and Normandy (), Scotland, Wales and Southern England (), Southern Scandinavia and Northern Germany () The main purpose of these journeys is the study of the European atlantic heath vegetations, a later paper will be dedicated to which I am much indebted to the State Institute for Nature Conservation Research (RIVON), the French Government and the Netherlands Organisation for the Advancement of Pure Research (ZWO), for financial support It is a pleasure to thank Mr C Altehage, Dr F Runge, Mr R E Parker, Dr A Dizerbo, Dr J M Gdhu, Dr C H Mr Gimingham, G Argent, Dr N Maimer, Fil lie F Andersson, Fil lie J Ericson, Fil mag M Sonesson for their valuable advice and practical assistance REFERENCES Bocher, T W Biologiske Skrifter II : 0 Damman, A W H Botaniska Notiser 0: Gimingham, C H Journal of Ecology, ; Schubert, R 0 Die zwergstrauchreichen azidiphilen Pflanzengesellschaften Mitteldeutschlands Pflanzensoziologie Bd II Jena Smidt, J T de Wentia : Stoutjesdijk, Ph Wentia :